What is ELISA?

ELISA is a robust, high-throughput immunoassay that leverages the specificity of antibody-antigen interactions to detect target molecules in complex mixtures such as serum, cell lysates, or tissue extracts. The assay is performed on a microplate, where capture antibodies are immobilised on the surface to bind the target analyte. After washing, detection antibodies conjugated to an enzyme (e.g., horseradish peroxidase or alkaline phosphatase) are added. A chromogenic substrate is then applied, producing a measurable colour change proportional to the amount of target present.

How does ELISA work?

The process begins with coating a microplate with a capture antibody specific to the target antigen. The sample is added, allowing the antigen to bind. Unbound material is washed away, and a detection antibody—also specific to the antigen—is introduced. This detection antibody is linked to an enzyme that catalyses a colour-producing reaction when a substrate is added. The intensity of the colour, measured spectrophotometrically, correlates with the concentration of the analyte in the sample. ELISA formats include direct, indirect, sandwich, and competitive, each suited to different experimental needs.

What are the applications of ELISA?

ELISA is extensively used in clinical diagnostics (e.g., HIV, hepatitis B/C, Lyme disease), pharmaceutical development (e.g., therapeutic protein quantification), food safety (e.g., allergen detection), and environmental monitoring. Its sensitivity, specificity, and adaptability make it a cornerstone of modern biomedical research and quality control. The assay is compatible with automation and is often used in conjunction with other techniques such as HPLC, NMR, and PCR for comprehensive analysis.

Related concepts

ELISA is frequently used alongside other immunoassays like Western blotting and immunohistochemistry. It is also integrated into regulatory workflows governed by ISO, GHS, and REACH, particularly in the validation of diagnostic kits and biologics. Quality control relies on CoA, SDS, and reference standards such as USP, BP, and EP.